The present invention generally relates to frozen desserts and their preparation. More particularly, it relates to nonfat frozen desserts with the organoleptic characteristics of high fat ice creams and related frozen desserts. The present invention also relates to the methods for making these nonfat frozen desserts, and the dry blends used in preparing the nonfat liquid compositions or mixes from which the frozen desserts are produced.
"Frozen dessert" is a generic term applied to a wide variety of products including ice cream, hard frozen and soft serve ice milks, sherbets, mellorines, water ices, and hard and soft frozen yogurts. Federal and state standards exist for all of these products with the exception of frozen yogurts where no federal standards currently exist and only a few states have developed compositional standards.
Among the "dairy" frozen desserts, minimum standards exist for milk fat and/or milk solids content. For example, ice cream must contain not less than 10% milk fat and 20% total milk solids (comprised of the total of milk fat and milk solids non-fat, "MSNF"); ice milk must contain 2 to 7% milk fat and not less than 11% total milk solids; and sherbet must contain 1 to 2% milk fat and 2 to 5% total milk solids.
All of these products are prepared from a mixture of dairy ingredients (mellorine being the exception with vegetable fat substituted for butterfat), sweeteners, stabilizers, emulsifiers, and flavorings with or without colorings. The ingredients are pasteurized in liquid form, homogenized, flavored, and frozen under agitation to incorporate air, then hardened and stored frozen for distribution and consumption.
Frozen yogurt desserts involve the addition of yogurt after pasteurization of the other ingredients where viable live organisms normally contained in non-frozen yogurt are deemed of value when present in the final product.
The formulations, preparation methods, and descriptions of the various frozen desserts mentioned above are described generally in W. S. Arbuckle's "Ice Cream", fourth edition, The AVI Publishing Company, Inc., Westport, Conn., 1986, the disclosure of which is incorporated by reference herein for purposes of establishing the background of the invention.
"Premium" and "Super Premium" ice creams are identified by higher butterfat levels of 14-18%, high total solids from the higher percentages of butterfat, milk, solids, and/or sweeteners used, and are frequently lower in overrun (less air being incorporated into the frozen product). A disadvantage with these products are; high price, a large number of calories, and a high level of cholesterol.
Ice creams and other whipped frozen dairy desserts are actually rather complicated foams consisting of air bubbles surrounded by a partly frozen emulsion wherein ice crystals and solidified fat globules are embedded in the unfrozen water phase. Estimates of the sizes of the coarsely dispersed structural components of ice cream vary. Ice crystal sizes are reported to vary in size between 20 to 60.mu. in diameter and to be situated approximately 7.mu. apart; air cells are reported to range in size between 10 to 175.mu. and to be situated about 125.mu. apart; and solidified fat globules are reported to vary in size from 0.2 to 2.0.mu. and to form agglomerations providing a "skin" around trapped air cells. See, "Fundamentals of Dairy Chemistry", 2nd Ed., 1983, Webb, B. H., et al., eds., Avi Publishing Company, Inc., Westport, Conn., at pages 896-913, the disclosures of which are incorporated by reference herein for purposes of establishing the background of the invention.
It is well known that the fat content of frozen dairy desserts plays a substantial role not only in the body and texture of the product, but also its flavor characteristics. Smoothness of ice cream texture is essentially inversely proportional to the average size of ice crystals. Increases in the milk fat content for virtually any given frozen dessert formulation will both decrease the ice crystal size and the distance between crystals. For example, the so-called "premium grade" ice creams are essentially characterized by higher than standard milk fat contents in the range of 15 to 18% and are recognized as products of correspondingly increased palatability and smoothness and enhanced body and texture in comparison to standard grade ice cream and dairy dessert products having lower fat contents.
Therefore, numerous attempts have been made to provide nonfat frozen desserts which exhibit organoleptic qualities of conventional or even premium and super premium ice creams. Prior to the present invention, nonfat, cholesterol-free frozen desserts have not been able to achieve equivalent organoleptic qualities.
"No-fat" or "nonfat" frozen desserts contain no added butter or vegetable fat and have a fat level of less than 0.5 percent by weight. When the fat is replaced, additional nonfat milk solids, sweeteners, stabilizers and/or emulsifiers must be supplied to yield similar body and freeze down characteristics.
The removal of fats from frozen desserts necessitates replacing them with other ingredients to facilitate whipping of the products and to achieve their stability during distribution and storage. Fat free frozen desserts are very complex systems in which gas bubbles are dispersed in a continuous liquid phase known as lamellae. Certain proteins are effective foaming agents essential to obtaining a desired overrun, i.e. a desirable degree of aeration, in frozen desserts. Other proteins are able to form protective layers/barriers separating entrapped gas bubbles from lamellae by absorbing at the gas/liquid interface. Whey proteins, egg white proteins, casein micelles, .beta.-casein and others possess good foam-forming properties. The glycoproteins of egg whites (ovomucoid and ovalbumin) help stabilize foams because they absorb and retain water in the lamellae. Egg whites reportedly have little effect on conventional frozen desserts such as ice cream, probably due to the fact that the fat globules break down the egg white foam very readily. For this reason manufacturers of angel food cake mixes point out that the mixing bowls used for whipping up an angel food cake mix should be totally free of fat residues.
Difficulties in producing nonfat dairy based aerated frozen desserts are compounded when the fat solids are replaced by lower molecular weight ingredients which affect the freezing point and the meltdown during consumption. Furthermore, distribution of these nonfat aerated frozen desserts has typically shown more vulnerability to heat shock instability because of the lack of fat.